Embryo and Aleurone Layer of Hordeum. 
1165 
TABLE XXX. 
Influence of Dextrose on the Amyloclastic Secretory 
Function of the Barley Embryo. 
Chilian barley. Seeds steeped successively in (1) CuSO. t 10 %, (2) water; 24 hours in each 
reagent; 40 embryos each culture. Culture period, 10 days. 
Exp. Medium. 
1. °'55 % asparagin-M.S. (control) 
2. °-55 % asparagin-M.S. + 1 % dextrose 
3. i* 1 % asparagin-M.S. (control) 
4. 1 *i % asparagin-M.S. + 1 % dextrose 
Dextrose in the concentration employed in the foregoing experiments 
obviously diminishes the secretion of amylase by the embryo; not only, as 
Experiments 2 and 4 very clearly show, is the amount of enzyme found in 
the culture medium reduced, but in the objects themselves this also holds. 
There is, apparently, in these instances where either cane sugar or dextrose 
is available, no need for internal digestion, and hence the secretion of enzyme 
is absent or greatly diminished. The embryo, therefore, regulates its 
secretory mechanism largely according to the nature and constitution of the 
supply of external nutriment. 1 2 
Luxuriant growth of the embryo invariably occurs on both solid and 
liquid media with the addition of either of the carbohydrates mentioned. 
Comparison of the weights of the embryos (Experiments 3 and 4) affords 
typical examples of the increased assimilation and growth which take place 
in these circumstances. 
This latter observation at one time suggested that possibly active 
secretion took place in these cells, but was wholly intracellular, the 
rapidly absorbed cane sugar undergoing transformation and condensation 
in the epithelial cell, and the starch thus formed being subsequently hydro¬ 
lysed into readily diffusible sugar and translocated to the actively growing 
parts of the young plantlet. 
The absorption of nutriment by the isolated embryo under the artificial 
cultural conditions described is extremely rapid, as shown by the turgid 
appearance presented by the scutellum. Unless assimilation keeps pace 
with this enhanced absorption, the osmotic forces \yithin this tissue reach 
such a high value that the organ ruptures. This frequently occurs in the 
case of Zea (maize) seedlings, the scutellum being split right across, a deep 
1 Desiccated 6 hours at 30° C. 
2 Sections through the scutellum of embryos nourished with these carbohydrates singly show on 
treatment with iodine the presence of starch in quantity in the scutellar tissues. Similar microtomed 
fixed and stained sections, especially those prepared from embryos removed during the first 48 hours 
of culture on cane sugar media, show starch granules in the columnar epithelial cells. 
40 
Amylase per 20 embryos 
per hour in :— 
Medium. Objects. 
(equivalent to mg. of Cu.) 
219 22 
81 14 
205 29 
9 2 H 
Weight of 40 
embryosP 
' mZ 
60 
185 
